Personality and IQ: Do Older Siblings Have the Advantage?

First Posted: Jul 16, 2015 04:50 PM EDT

Were you born first, second, or third? Apparently, it doesn't matter. Scientists have found that birth orders don't necessarily affect your life down the line.

In this latest study, the researchers examined 377,000 high school students and looked at their IQs and personality. They also accounted for potentially confounding factors, such as a family's economic status, the number of children and the relative age of the siblings. For example, wealthier families tend to have fewer children than other families and also have a higher proportion of first-borns who also have access to more resources that may influence their IQ or personality.

So what did they find? Those who are born first do enjoy a one-IQ-point advantage over those who are born later. However, while this difference is statistically significant, it's essentially meaningless. There also were consistent differences in personality; those who were born first tended to be more extroverted, agreeable and conscientious and had less anxiety. With that said, the differences were also "infinitesimally small" and amounted to a correlation of .02.

"In some cases, if a drug saves 10 out of 10,000 lives, for example, small effects can be profound," said Brent Roberts, one of the researchers, in a news release. "But in terms of personality traits and how you rate them, a .02 correlation doesn't get you anything of note. You are not going to be able to see it with the naked eye. You're not going to be able to sit two people down next to each other and see the differences between them. It's not noticeable by anybody."

The findings reveal that any differences between people who are born first and those who are born after are negligible. While there are minute differences, they won't impact a person later on in their lives.

The findings are published in the Journal of Research in Personality.